Several lines of investigation suggest that dysregulation of gap junction intercellular communication, or gap junctional remodeling, contributes to the substrate for ventricular arrhythmias. Using the canine infarct model, investigations in this Program have shown that changes in the structural location of gap junctions and the electrophysiological properties of gap junctions are associated with functional lines of block in reentrant circuits. Similar gap junctional remodeling has also been observed in human ischemic cardiomyopathy and in our studies of genetically modified mice with ventricular tachycardia and sudden cardiac death. Myopathic hearts, however, show a multitude of structural and functional perturbations, thus, the unique arrhythmias has been difficult to study in isolation from other contributory factors. The goal of the studies described in this proposal is to understand the molecular mechanisms of gap junctional remodeling and to determine the specific contribution of dysregulated intercellular coupling to the formation of the arrhythmogenic substrate. The applicant has, therefore, begun to elucidate mechanisms controlling gap junctional expression and remodeling and discovered that the Wnt signaling cascade, acting through beta-catenin via duel transcriptional and post-translational mechanisms, is an important regulatory pathway controlling connexin43 expression. Furthermore, they have prepared several conditions gene-targeted murine models to elucidate the role of remodeling in formation of the arrhythmogenic substrate. Their goals in junctional remodeling, conduction abnormalities and arrhythmogenesis, using gene-targeted and chimeric mice; 2) to determine the role of beta-catenin mediated signaling and its relationship with other signaling pathways in the regulation of Cx43 expression in normal and remodeled cardiomyocytes and hearts; 3) to determine the mechanisms responsible for gap junctional reentrant excitation appears to be related to changes in gap junction distribution. Elucidation of the mechanisms regulating gap junctional remodeling and its role in the arrhythmogenic substrate have significant implications for novel pharmacotherapy of lethal cardiac arrhythmias.